U.S. patent number 4,132,421 [Application Number 05/822,110] was granted by the patent office on 1979-01-02 for shaft seal.
This patent grant is currently assigned to Federal-Mogul Corporation. Invention is credited to George L. Corsi, Stanley N. Smith.
United States Patent |
4,132,421 |
Corsi , et al. |
January 2, 1979 |
Shaft seal
Abstract
An improved metal encased radial-type oil shaft seal of either
single or dual lip construction wherein the primary seal lip is
polytetrafluoroethylene -- or the like and is bonded and
mechanically interlocked to the metal case by an elastomeric
material.
Inventors: |
Corsi; George L. (Southfield,
MI), Smith; Stanley N. (Farmington, MI) |
Assignee: |
Federal-Mogul Corporation
(Detroit, MI)
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Family
ID: |
24195602 |
Appl.
No.: |
05/822,110 |
Filed: |
August 5, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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550066 |
Feb 14, 1975 |
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Current U.S.
Class: |
277/565; 277/559;
277/924; 277/570; 277/575; 277/577 |
Current CPC
Class: |
F16J
15/328 (20130101); F16J 15/3284 (20130101); Y10S
277/924 (20130101) |
Current International
Class: |
F16J
15/32 (20060101); F16J 015/32 () |
Field of
Search: |
;277/227,215,184,183,186,166,27R,233,165,182,134 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Aegerter; Richard E.
Assistant Examiner: Footland; L.
Attorney, Agent or Firm: Hess; Robert F.
Parent Case Text
This is a continuation, of application Ser. No. 550,066, filed Feb.
14, 1975, now abandoned.
Claims
We claim:
1. An oil seal adapted to be press fitted into a bore of a housing
member through which a rotating shaft extends and wherein the seal
is to be mounted on such shaft in interference fit therewith so as
to exclude the passage of oil along the shaft comprising,
a relatively rigid metal case means,
a wafer-like seal element including an annular frustoconically
shaped portion defining a seal lip at one end adapted for
interference fit with a shaft,
said wafer-like seal element being of uniform cross-sectional
thickness and being of a non-elastomeric material other than metal
and heatably unbondable thereto,
a flange portion of said seal element being in juxtaposition with
said case means,
elastomeric bonding means for securing said seal element to the
case means, said bonding means including a main body portion
opposite the flange portion of said seal element from the case
means,
said flange portion of said seal element including a plurality of
passages in and circumferentially spaced about the flange portion,
and said elastomeric bonding means further including secondary
portions extending from the main body portion and through each of
said plurality of passages and being bonded to the case means
whereby said seal element is fixed in place relative to the case
means and is prevented from rotating relative thereto.
2. An oil seal as defined in claim 1, wherein:
said case means includes an outer cylindrical portion and a radial
flange depending from one end thereof,
said radial flange being of stepped configuration and including a
lower radial portion, an intermediate cylindrical portion, and an
upper radial portion,
said lower radial portion and said intermediate cylindrical portion
defining a counterbore, and
said flange portion of wafer like seal element and said elastomeric
bonding means being located within said counterbore.
3. An oil seal as defined in claim 1 further including a second
seal lip means, said second seal lip means being of elastomeric
material and of annular shape.
4. The oil seal of claim 3 wherein said second seal lip is integral
with said elastomeric bonding element means, and is of
frustoconical shape with the radially inwardmost end of said second
seal lip means being directed in a direction axially opposite that
of said seal element.
5. The oil seal as defined in either claim 1 wherein said seal
element is polytetrafluoroethylene.
Description
BACKGROUND OF THE INVENTION
This invention relates to oil seals, particularly shaft seals
wherein the primary sealing lip element is an annular wafer shaped
article which completely surrounds the shaft to be sealed and is in
light engagement therewith at its inner annulus, or seal lip as it
is commonly referred to.
Typically the aforesaid primary sealing lip element is part of a
metal cased assembly which is press fitted into a shaped housing
bore. The entire metal cased seal assembly ordinarily comprises a
cup shaped metal case having an outer cylindrical portion adapted
for press fitted engagement with the bore of the housing and a
radical flange extending radially inward from one end thereof, a
seal element, a gasket between the seal element and radial flange
of the cup shaped metal case, and a second metal case having a
radial portion backing up the seal element axially inward of the
first metal case radial flange. The two metal cases are crimped or
otherwise tightly secured to one another in such manner that the
seal element is likewise secured between the radial flanges of the
two metal case member.
Typical of seals of this construction is that shown in copending
patent application Ser. No. 426,373, filed Dec. 19, 1973, now U.S.
Pat. No. 3,857,156, and assigned to the assignee of this
invention.
The latest development in this type of seal includes making the
primary sealing element of polytetrafluoroethylene or the like and
incorporating therein unidirectional and bidirectional hydrodynamic
oil feedback features which prevent oil from leaking past the lip
portion of the sealing element. For example, a spiral groove or
flute located on the air side of the sealing element in the area of
the lip portion will prevent oil leakage in one direction of shaft
rotation such as shown in the aforesaid pending patent application.
Similarly, bidirectional hydrodynamic features can be provided with
sealing element configurations such as shown in copending patent
application Ser. No. 541,926, filed Jan. 17, 1975, now U.S. Pat.
No. 3,984,113 and assigned to the assignee of this invention.
These seals work well for the intended purpose but assembly
includes a great number of separate fabrication operations.
Further, the design of such seals does not lend itself to
adaptation for a dual lip seal and consequently their use is
limited. Also, applicants desired a design which would reduce the
raw material requirements so as to minimize as much as possible the
current problems of availability and cost.
SUMMARY OF THE INVENTION
In the present invention an oil seal is constructed of a single
metal case member and a wafer like annular lip seal element secured
to the metal case by an elastomeric material. The metal case
includes an outer cylindrical portion and radial flange depending
inward from one end thereof which is of stepped configuration. This
in turn provides in effect a counterbore in which is accurately
located the radially outermost portion of the seal element as well
as the elastomeric bonding material, or its equivalent. The
securement of the lip seal element to the case is enhanced by
providing a plurality of holes or slots in the seal element in the
area where it is backed by the metal case so that the elastomer
fills such holes. This gives a mechanical interlock with the seal
element as well as an increase in the bonding strength with the
metal case.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a view in end elevation of a radial type shaft seal
embodying the principles of the invention.
FIG. 2 is an enlarged view in section taken through the seal along
line 2--2 in FIG. 1.
FIG. 3 is an enlarged view in section similar to that of FIG. 2 and
illustrating a modification thereof commonly referred to as a dual
lip cup case seal.
FIG. 4 is an end elevation view of the polytetrafluoroethylene
washer or wafer constituting the main seal lip in accordance with
the invention and prior to its insertion in the mold cavity.
FIG. 5 is a view in elevation and section of the mold cavity with
the seal elements located therein just prior to closing the mold
and completing fabrication of the seal shown in FIG. 3 in
accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 and 2 show a radial type oil shaft seal of one preferred
form embodying the principles of the invention. The seal 10 is of
the single lip type and includes a single metal case 12 having a
radially outermost axially extending cylindrical portion 14 and a
stepped radial flange 16 extending inwardly from one end thereof.
Radial flange 16 includes lower radial portion 18, an intermediate
axially extending cylindrical portion 20, and an upper radial
flange portion 22 depending in from the axial inboard end of
axially extending portion 20. These latter two members, namely the
intermediate cylindrical portion 20 and upper radial portion 22
form a counterbore. Located within this counterbore and secured
against flange portion 22 by means of an elastomeric bond is a flat
radial outer portion 24 of seal element 26, preferably made of
polytetrafluoroethylene, and which also has a frustoconical portion
28 which constitutes the lip portion of the seal element. The flat
radial outer portion 24 includes a plurality of holes 30 equally
spaced about its circumference and filled with an elastomeric
material, (preferably Buna-n), which forms the elastomeric radial
reinforcement member 32. The elastomeric member 32 is bonded to the
intermediate cylindrical portion 20 of the metal case at its
circumference as well as at each interface 34 with the upper radial
flange portion 22.
As desirable for some applications, the air side surface 36 of the
frustoconical portion 28 of seal element 26 may have a spiral
groove 38 leading outward from innermost edge 40 of the seal. This
groove 38 is made so that during rotation of the shaft in a
particular direction, the groove tends to return any oil which may
leak along the shaft, due to scratches in the shaft or minor
imperfections in the shaft or even in the shaft sealing element,
though most of the leakage occurs in this instance from the shaft
imperfections. As in all hydrodynamic seals, the purpose of the
groove 38 is to return the oil beneath the seal lip 40 and back to
the oil side of the seal.
When the seal 10 is installed, there is shaft interference which
flexes the inner portion 28 and makes a portion thereof
substantially cylindrical for a short distance; that is why the
spiral groove 38 extends a substantial distance along the face,
because the degree of shaft interference is somewhat
indeterminate.
It should perhaps be emphasized that the stepped configuration of
radial flange 16 is important for several reasons. First of all, it
provides a method of accurately locating the flat radial outer
portion 24 of the seal element which it will be noted has already
been pierced to its final inner diameter. Any eccentricity or
offset in location of the seal element within the metal case will
naturally result in the lip portion of the seal element being
offset from the shaft it is to seal. And this of course might well
result in an oil leak. Another advantage resulting from the stepped
configuration is that this accurate location of the seal element
can be effected with much less material usage than would be
required if it were necessary to locate the seal element with
respect to the radially outermost cylindrical portion 14. Less
bonding material 32 is required for the same reason. It is likewise
obvious that the stepped configuration allows metal case 12 to be
sized consistent with those of conventional molded lip seals and
therefor the seal of our invention can be used as a replacement
thereof without the necessity of further design changes, such as
resizing the shaft housing seal bore, and the like.
FIG. 3 shows a second preferred embodiment of an oil shaft
embodying the principles of the invention. It is similar in
construction in all respects, with one exception, to the seal shown
in FIGS. 1 and 2. Therefore like numerals are used to indicate like
features. The distinguishing feature of the seal of FIG. 3 is that
it is a dual lip type seal. The secondary lip 42, which is provided
for excluding dust and dirt from the primary seal lip, may be an
integral portion of elastomeric member 32. As seen it is likewise
frustoconical in shape but extends in an axial opposite direction
than frustoconical portion 28. The lip 42 extends downward in the
direction of the shaft on which it is to be installed a distance
sufficient to make light sealing contact therewith. Lip 42 need not
extend inward as far as innermost end 40 of seal element 26, and it
is preferred that it does not do so.
FIG. 4 illustrates the polytetrafluoroethylene seal element 26
prior to assembly in the mold to the case. As such it is simply an
annular frustoconically shaped disc with a plurality of holes
spaced about the radially outermost portion. The most convenient
method of manufacturing would be to stamp the annular disc from
sheet stock and in the same operation to pierce the holes 30. The
spiral groove 38 may, during this same operation or subsequently,
be coined. The frustoconical shape may likewise be imparted to the
flat wafer by a suitable coining operation. The frustoconical
performing could also be accomplished in the mold cavity, if
desired.
Assembly of the oil seal is accomplished in a mold such as shown in
its fully open position in FIG. 5.
The mold assembly comprises the usual elements and arrangement
thereof conventional to those used in the forming of molded
elastomeric lip seals such as shown for example in U.S. Pat. No.
2,982,999 and includes lower mold 50, mold core 52, and upper mold
54, all of which when in the fully closed position define a cavity
which determines to which areas of the seal the elastomeric prep
material will flow. The mold core 52 is located on a cap screw 56
having a lower head portion 58 which arrests the mold core and
upper mold. Lower mold 50 includes an upper portion which is shaped
complementarily to that of the stepped metal case 12' so that the
latter may be securely located with respect thereto during
assembly. Upper mold 54 includes a shoulder portion 60 adapted to
abut an adjacent portion 61 of mold core 52. The upper mold 54 and
mold core are made of separate pieces primarily for ease of
machining the complex shaped cavity portion. They may be considered
as fixed relative to one another, however gas generated during the
molding operation is allowed to escape from the mold cavity and out
of the mold assembly by passing upwardly between surface portions
60 and 61. Shoulder screw 62 retains Belleville spring 64 which in
turn allows alignment of the lower mold 50 with the mold core in
the closed position.
The oil seal, which as shown in FIG. 5 is of the dual lip type
depicted in FIG. 3, is assembled by first locating metal case 12'
with seal element 26' and an annular elastomeric prep all situated
within the stepped portion of the metal case on lower mold 50.
Inner wall 51 of the lower die is shaped complementarily to the
frustoconical portion 28 of the seal element so that when the mold
is closed the respective elements of the seal will not be
dislodged. The mold which operates at an elevated temperature
equaling the cure temperature of the elastomeric prep is then
closed. The prep flows through holes 30 in the seal element and
forms a bond with the metal case at the intermediate axial portion
and at the inner radial flange portion in the area of holes 30. If
desired, mold core 52 may include a raised annular rib 66 which
will coin the seal element and thereby eliminate elastomeric flash
which might otherwise be present if the prep were to flow past that
particular portion of the mold core which engages the radially
outermost portion of the frustoconical portion 28.
As an alternative molding operation one may begin with a flat
coined sealing element and coin or otherwise form the frustoconical
shape of the sealing element in the mold simultaneous with the
molding operation.
To those skilled in the art to which this invention relates, many
other changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the spirit and scope of the invention. The
disclosures and the description herein are purely illustrative and
are not intended to be in any sense limiting.
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